Shoe sole composition



May 12, 1953 GATES 2,638,457

S HOE SOLE COMPOSITION Filed Oct. 2, 1945 [MODIFIEIFI LSTYRENEI LBUTADIENEW liATALYSfl EMULSIFIER] l 4 STYRENE WATER PHASE EMULS'ON PHASE COPOLYMERIZATIOIU REACTION STOPPED ANTI-OXIDANT 4 I COAGULATION I l WASHING DRYING BUTADI ENE STYRE NE CQPOLYMER I-ADDITION oF' CELLULOSIC FLocfl COMPOUNDING I SI Gegrge HTGates I VULCANIZATE I Patented May 12, 1953 SHOE SOLE COMPOSITION George H. Gates, Cuyahoga Falls, Ohio, assignor to Wingfoot Corporation, Akron, Ohio, a corporation of Delaware Application October 2, 1945, Serial No. 619,876

This invention relates to a new vulcanized shoesole composition in sheet form comprisingasubstantial and effective amount of an inorganic filler and a cellulosic flock material and as a binder therefor the vulcanizate resulting from thevulcanization of a mixture of rubbery copolymer and resinous copolymer of butadiene-LS and styrene.

The drawing is a flow chart showing the process ofproducing the blend and canizate of this invention.

the vulbeen considered a more useful material than naturalrubber, although rubber possesses qualities '15 rendering it desirable for use in footwear. A material which possesses the desirable charac-- teristics of leathenqtogether with the desirable characteristics of rubber, and without the undesirable characteristics of either, would constitute a great advance in the manufacture of shoe soles and in large measure increase foot comfort...

7 Claims. (Cl. 260-17.4)

In the manufacture of shoe soles, leatherhas .It is welleknown that leather is. subject to dey terioration by moisture because of the constant wetting and drying. action that leather soles undergo which soon cause them to become stiff,

thereby interfering with proper foot comfort.

Rubber, .On the other hand, is not so affected, but. presents other disadvantages as a shoe sole;

for v.example in the matter of the transmission ofheat from the walking surface to the. foot. iv

Rubber does not possess sufi'icient stiffness for.

foot comfort unless excessively loaded with pig.- ments. Inan attempt to impart the necessary stiffness to rubber for shoe sole use, various pigments have been used, including carbon black,

whiting, etc,, but the proper degree of stiffness is not obtained until such a large amount of.

stiffener or pigment has been. incorporated that the pigmented rubber becomes dead in the sense that it has little or no resiliency or springiness.

The pigmented rubber is also too heavy for practical shoe sole ,use.

badly marksthe surface walked upon.

Ordinarily, rubber, natural or synthetic, is too Where carbon black is used as the stiffener, the highly pigmented rubbe flabby or soft for shoe sole use, without loading and too difficult to cement to the shoe uppers.

Furthermore, when stitched, the sole. tends. to:

roughen out in a hill and valley effect due to the tension put upon the material by the stitches.

Also, the stitches tend to cut through the. ma-

terial. Ultimately, sore .feet may be caused'by.

the creep characteristics of such a soft and flabbyimaterial, Again, shoe soles made of. rub.-

v 2 ber cannot be made pigments because the resulting pigmented rubber has a tendency to flex-crack under higher p gment loadings. I

It has now been discovered that the synthetic rubber from butadiene-1,3 and styrene, heretofore ordinarily unsuitable as a shoe sole material, may be made more desirable than leather for shoe sole use when the rubber is blendedwith a resinous diene-vinyl copolymer and com- When this rubber is blended and compounded with pounded with a cellulosic flock material.

these materials, an unexpected and highly desirable result is produced in that the resulting material has an exceptional leathery feel, to-

gether with the proper resilience and springiness. The rubber component of the new composition is a rubbery copolymer resulting from the polymerization of a. mixture containing as the essential copolymerizable monomers butadiene-v 1,3 and styrene or a substituted styrene and having an elongation of at least 300% and the ability to retract to substantially its original shape.

The resinous component of the blend may vary from a hard, brittle resin to a stiff, flexible material depending upon the ratio of butadiene-1,3 and vinyl aromatic monomer present in the mixture polymerized. This resinous characteristic" is present in the product resulting from the reaction of a mixture of butadiene-1,3 and vinyl aromatic monomer when present in a ratio between about 30/70 and about 5/95; '1. e.,about 30 to 5 parts of butadiene-1,3 to about '70 to 95 parts of vinyl compound (e. g., styrene).

The vinyl aromatic monomer of the resin may also be referred to as being an alpha, beta uni saturated aliphatic substituted aromatic monomer, specific examples being styrene, the substituted styrenes, e..g., metachlorostyrene, p-

chlorostyrene, isomeric dichlorostyrenes, alkyl styrenes, e. g., methyl styrene, isopropyl styrene,

and vinyl naphthalene, etc. A particularly desirable class of these monomers is constituted by the vinyl aryl monomers, the desired being styrene.

The following description illustrates generally the preferred conditions to be employed in producing the resin component.' Generally the drawing shows that the copolymerization is carried out in the emulsion stage in which a styrene I styrene, is I reacted with butadiene-1,3 in the presence of'a. -,water phase, including. a catalyst,- an emuslifier phase, including a modifier and harder than about -80 Shore hardness by the use of ordinary rubber member 1 and water. The copolymerization is continued at a temperature necessary to efiect reaction of the styrene with butadiene until the desirable hydrocarbon conversion is reached. The resulting latex is then coagulated and the coagulum is washed and dried. Where it is desired to stop the reactionat a certain percent hydrocarbon conversion value, an antioxidant is introduced into the latex in sufficient amount to terminate the reaction and to protect the resulting cagulum against deterioration by oxidation.

A more specific example illustrates the; copolye merization of a styrene phase, inc1uding,85 parts of styrene and 0.1 part of dodecyl mercaptan with parts of butadiene in thepresence of a water phase including 200 parts of water, 5 parts of sodium rosinate and 0.1 part ofzpotassiumpere sulfate at a temperature of 125 F. for a period. of time to form a latex having a solids content of 325%, after which time'0.5% of phenyl betanaphthylamineis introduced into the reaction: The latex is precipitated by the addition of -a 3 commercial alum solution,- the resulting coag ul-u'm being washed withwater anddried' to-produo e a resin having a softening pointof 62 0;

Any; suitable modifier may be added to the styrene phase.- Suitable-modi-fiers include thosegenerally referred to as mereaptans containingat least six oarbon atoms and" particularly suchmercaptans as isohexyl-y octadecyl-, and dodecylmercaptan. Otherdesira-ble modifiers-are-the diallsyl polysulfides, the tertiary alkyl meroaptans; and the dialkyl Xanthogen disulfides.

The modifier-may beadded in an amount betweenfabout--0.05% and about 3.0%; preferably in an amount-between about 0.08%.1and about 2.0%, and it has been found" particularly desirableto use about 0.1% in each case on the .combined weight of the aryl and jdiene components used. The modifiers act toincrease the solubility .33 of the resulting resin in suchsolvents'as benzene and toluene andalso adjust the-degree of stifiness; ofthe resin. The greater theamount'of modifier,v I the greater thesolubility and the'softer"the re-, sulting resin. 4 r

The water phase includes a catalyst,'water and, an emulsifier. Suitable catalysts that maybe, used are potassium persulfate, benzoyl' pero xide, hydrogen peroxide, perborates, percarbonate1s The catalyst may be used in an amount between m about 0.1% and about 1%. Typicalemulsifl'ers, are those which may be generally referred'tolas, the iatty acid soaps, e. g., sodi um stearate andthje, rosin acid soaps, e. g., sodium rosinate, and'the alkalrmetal salts of alkali; sulfuric acid'iesters, e. g., sodium lauryl sulfate, and the alkalijimetal salts of alkyl aryl sulfonates, e. g., sodium,dodecylbenzene sulfonate. The emulsifier may be present, in amount between about 0.1% and about 5%;

Water is present in' an amount based upon the total amount of monomers beingreacted and may be used in a monomer/water ratiobetween' about; 100/60 to about 100/200." Generally, the copqlyr, merization is carried out at a temperature between about C. and about'70-:C; for a period. of time between about 4 hours and about 100' hours, depending upon the percent conversion desired, the charged monomer ratio; the-catalyst used. and the type of monomerspresentv- The butadiene-styrene rubber-isblended withthe-resinous .copolymer and compounded with a cellulosic flocbmaterial and with asubstantial and effective. amount of: inorganic fillingrnaterial and a vulcanizingiagent and vulcanized toproduca the;,shoe sole, material of this sinventione A synthetic rubber which is admirably adapted for this blending and compounding is the one resulting from the copolymerization of butadiene- 1,3 and styrene in which the butadiene is present in a predominant amount, and particularly where the butadiene-styrene ratio ranges from about /40 toabout /15.

A desirable shoesole material is produce when blending the resinou material with a rubber in aresin-to-rubber ratio from between about 5/95 to about 75/25.

Alttypicallblending formula is one in which about parts of the rubber is blended with between ab'outt25ito about 100 parts of the resin andi-b'etweenzabout 10 and about 25 parts of a cellulosic flock material. This composition may' thentb'edurtherr compounded with suitable accelerators, softeners, sulfur and fillers to produce a vulcanizable shoe material which may then be vulcanized and cured at a temperature between about-300 and about 340 11 fora periodot timebetweenabout =10 mi'nut'esand about 1"'=hour* to produce ashoe -sol=material hav-ir1ggtl-ierleisii able characteristics mentioned" hereinbeffirer A-representative compounding formula-is as# follows:

Parts-by weight) Rubber 10G Dione-vinylresinous'material; 25 100 Cellu1osic flock material'i 10 25 Sulfur Organic accelerator (Tuads, Captax,

etc.) 1 2 Zinc oxide 3 :5 Filler (clay, whiting, sile'ne," etc.-'); 60- 100" Stearic'acid; 0:5 1 Softener (para-inn, pinetaryaspha-lt-dfiv atives; etc.)

,7 cured-sin the usual manner -to given vulcanized material: which then: may be' used' in* uncut 5 ram for :shoe-soles or may be -precut into'standardshoe sole sizes, 1:

It: has: been observed that the-presence of 'the' cellulosicflock material is essential i'n produ'cing-- a .,shoe.. soler; composition having 'the =desirabl properties mentioned. 1 For exar'npla tlie presence of this. 9 flockU material; .improveszathe non ski d properties-oi;;the:.. compositiomcomz icyi' and wetfi surfa-ces, andmateriallyareducesathe tendency fior the; compositiontoxfgrow i or fspread,-'.v byiwhibh quoted? :terms 1 is" meant that the dimensioii'al stability of the-sole composition has teemm proved: The flock also: improves the -"feel"of' the composition;-by -which" quoted' term is meant that the composition "has a fee}! *ofleath ery?" smoothness which is desi-rabl-edn asho'e'sol ma 4 teriali' The flock-" alsoprevents fieir crackingwf' the-= blend"a1one.-=-* The fidclrmaybe added'ln-itam amountibetween-about 10 parts' to about'zfi parts per 100 parts ofrubberused and it is preferred to use between about parts and about parts. Any cellulosic flock material may be used, including cotton and rayon flocks. Howeverpit is preferred to usethe rayon flock.

Suitable changes may be made in the details of the process without departing from the spirit or scope of the present invention, the proper limits of which are defined in the appended claims. I v p 1. A composition in sheet form comprising a filler including about 10 to about 25 parts of a cellulosic flock material together with a substantial and effective amount of mineral filler, and as a binder therefor the vulcanizate resulting from the vulcanization of (1) a rubbery copolymer of a major proportion of butadiene and a minor proportion of styrene, (2) 25 to 100 parts of a hard, thermoplastic resin obtained by copolymerizing a mixture of 70-95 weight percent of styrene and -5 weight percent of butadiene in aqueous emulsion in the presence of a substance which promotes the solubility of the resulting resin in benzene and selected from the group consisting of mercaptans containing at least six carbon atoms, dialkyl polysulfides, and dialkyl xanthogen polysulfides, and (3) sulfur as a vulcanizing ingredient for the binder, the parts being by weight per 100 parts by weight of rubbery copolymer.

2. A composition in sheet form comprising a filler including about 10 to about 25 parts of a cellulosic flock material together with a substantial and effective amount of mineral filler, and as a binder therefor the vulcanizate resulting from the vulcanization of (l) a rubbery copolymer of a major proportion of butadiene and a minor proportion of styrene, (2) 25 to 100 parts of a hard, thermoplastic resin obtained by copolymerizing a mixture of 70-95 Weight percent of styrene and 30-5 weight percent of butadiene in aqueous emulsion in the presence of a substance which promotes the solubility of the resulting resin in benzene and being an alkyl mercaptan having 6 to 18 carbon atoms, and (3) sulfur as a vulcanizing ingredient for the binder, the parts being by weight per 100 parts by weight of rubbery copolymer.

3. A composition in sheet form comprising a filler including about 10 to about 25 parts of a cellulosic flock material together with 60 to 100 parts of mineral filler, and as a binder therefor the vulcanizate resulting from the vulcanization of 1) a rubbery copolymer of a major proportion of butadiene and a minor proportion of styrene, (2) 25 to 100 parts of a hard, thermoplastic resin obtained by copolymerizing a mixture of 70-95 weight percent of styrene and 30-5 weight percent of butadiene in aqueous emulsion in the presence of a substance which promotes the solubility of the resulting resin in benzene and selected from the group consisting of mercaptans containing at least six carbon atoms, dialkyl polysulfides, and dialkyl xanthogen polysulfides, and (3) sulfur as a vulcanizing ingredient for the binder, the parts being by weight per 100 parts by weight of rubbery copolymer.

4. A shoe sole comprising a filler including about 10 to about'25 parts of a cellulosic flock material together with a substantial and effective amount of mineral filler, and as a binder therefor the vulcanizate resulting from the vulcanization of (1) a rubbery copolymer of a major proportion of butadiene and a minor proportion of styrene, (2) 25 to 100 parts of a hard, thermoplastic resin obtained by copolymerizing a mixture of 70-95 weight percent of styrene and 30-5 weight percent of butadiene in aqueous emulsion in the presence of a substance which promotes the solubility of the resulting resin in benzeneand selected from the group consisting of .mercaptans containing at least six carbon atoms, dialkyl polysulfides, and dialkyl xanthogen polysulfides, and (3) sulfur as a vulcanizing ingredient for the binder, the .parts being by weight per 100 parts by weight of rubbery copolymer.

5. A shoe sole comprising a filler including about 10 to about 25 parts of a cellulosic flock material together with a substantial and effective amount of mineral filler, and as a binder therefor the vulcanizate resulting from the vulcanization of (l) a rubbery copolymer of a major proportion of butadiene and a minor proportion of styrene, (2) 25 to 100 parts of a hard, thermoplastic resin obtained by copolymerizing a mixture of 70-95 weight percent of styrene and 30-5 Weight percent of butadiene in' aqueous emulsion in the presence of a substance which promotes the solubility of the resulting resin in benzene and being an alkyl mercaptan having 6 to 18 carbon atoms, and (3) sulfur as a vulcanizing ingredient for the binder, the parts being by Weight per 100 parts by weight of rubbery copolymer.

6. A shoe sole comprising a filler including about 10 to about 25 parts of a cellulosic flock material together with 60 to 100 parts of mineral filler, and as a binder therefor the vulcanizate resulting from the vulcanization of (1) a rubbery copolymer of a major proportion of butadiene and a minor proportion of styrene, (2) 25 to 100 parts of a hard, thermoplastic resin obtained by copolymerizing a mixture of 70-95 weight percent of styrene and 30-5 weight percent of butadiene in aqueous emulsion in the presence of a substance which promotes the solubility of the resulting resin in benzene and selected from the group consisting of mercaptans containing at least six carbon atoms, dialkyl polysulfides, and dialkyl xanthogen polysulfides, and (3) sulfur as a vulcanizing ingredient for the binder, the parts being by weight per 100 parts by weight of rubbery copolymer.

7. A shoe sole composition in sheet form comprising a filler including 10 to 25 parts of a cellulosic flock material, together with a substantial and effective amount of mineral filler and, as a binder therefor the vulcanizate resulting from the vulcanization of a mixture of (1) a rubbery copolymer resulting from the polymerization of a mixture containing 60 to weight percent of butadiene-1,3 and 40 to 15 Weight percent of styrene, (2) 25 to parts of a hard, thermoplastic resin obtained by copolymerizing a mixture of 70-95 weight percent of styrene and 30-5 weight percent of butadiene in aqueous emulsion in the presence of a substance which promotes the solubility of the resulting resin in benzene and being an alkyl mercaptan having 6 to 18 carbon atoms, (3) 2 to 3 parts of sulfur, (4) l to 2 parts of an organic accelerator, (5) 3 to 5 parts of zinc oxide, (6) 0.5 to 1 part of stearic acid, and (7) 5 to 20 parts of a softener, the parts being by weight and per 100 parts by Weight of rubbery copolymer.

GEORGE H. GATES.

(References on following page) R'ffii gs" Cit fed if tpeffil @jmgg p't'nt" FOREIGK PATENTS UNITED STATES PATENTS Nuniben, E untry Date Number Name t 345,939 Great Britain Mar. 16, 1931 2,029,371 Hicklrj Fe 4, 1936" 5 OTHER REFERENCES Guinzburg 5 1:. x .Fu w a 2,393,208 Wateim'ant a1. Jan, 15*, 1946'" gfiiifgfi g ggi i fi g 286- 2414803 DAl'elib Jan.' 28 1947 2 419 202 A" fi ltlfli wfianq okpn 1 4 7 214527999 i e 2" 1948. 1 published 1942 by R. T. Vanderbilt (30., N. 2:477316 YKT? 1 T 'T T 0' India Rubber World, January 1945, pgggfigl 5 1 7. 233 9 F 6",?" g 1951. India. Rubber World, February 19.45, 590. 

1. A COMPOSITION IN SHEET FORM COMPRISING A FILLER INCLUDING ABOUT 10 TO ABOUT 25 PARTS OF A CELLULOSIC FLOCK MATERIAL TOGETHER WITH A SUBSTANTIAL AND EFFECTIVE AMOUNT OF MINERAL FILLER, AND AS A BINDER THEREFOR THE VULCANIZATE RESULTING FROM THE VULCANIZATION OF (1) A RUBBERY COPOLYMER OF A MAJOR PROPORTION OF BUTADIENE AND A MINOR PROPORTION OF STYRENE, (2) 25 TO 100 PARTS OF A HARD, THERMOPLASTIC RESIN OBTAINED BY COPOLYMERIZING A MIXTURE OF 70-95 WEIGHT PERCENT OF STYRENE AND 30-5 WEIGHT PERCENT OF BUTADIENE IN AQUEOUS EMULSION IN THE PRESENCE OF A SUBSTANCE WHICH PROMOTES THE SOLUBILITY OF THE RESULTING RESIN IN BENZENE AND SELECTED FROM THE GROUP CONSISTING OF MERCAPTANS CONTAINING AT LEAST SIX 